1. Field of the Invention
The present invention relates to a fuel supply device used in a pressure accumulation fuel injection system of an internal combustion engine. Specifically, the present invention relates to a fuel filter that filters fuel drawn by a feed pump.
2. Description of Related Art
A pressure accumulation fuel injection system is known as a fuel injection system of a diesel engine and the like. As shown in FIG. 7, this system has a common rail 100, a fuel supply pump 110, an injector 120 and the like. The common rail 100 accumulates high-pressure fuel. The fuel supply pump 110 pressure-feeds the fuel to the common rail 100. The injector 120 injects the high-pressure fuel supplied from the common rail 100 into a cylinder of the diesel engine.
The fuel supply pump 110 of this system has a feed pump 140 that draws the fuel from a fuel tank 130. A fuel filter 150 is located upstream of the feed pump 140. The fuel drawn by the feed pump 140 passes through the fuel filter 150 and is filtered (for example, as described in JP-A-2004-316518).
In the case where the fuel filter 150 is located upstream of (on a suction side of) the feed pump 140, a fuel pressure (passing pressure) applied to the fuel filter 150 is low. Therefore, for example, if viscosity of the fuel increases and the fuel becomes wax-like when temperature is low, the fuel filter 150 will be clogged, and a flow rate will become insufficient immediately. As a result, there is a possibility that the fuel discharged from the fuel supply pump 110 becomes insufficient. In such a case, engine stall can be caused.
As shown in FIG. 8, another fuel injection system has a fuel filter 150 downstream of the feed pump 140. In the fuel injection system shown in FIG. 8, an entire quantity of the fuel drawn by the feed pump 140 passes through the fuel filter 150. Accordingly, the body size of the fuel filter 150 increases. In such a case, it is difficult to install the fuel filter 150 to a diesel engine having a tight space (for example, a diesel engine with a small engine displacement).